Butterfly valve

ABSTRACT

A portion of the one valve rod which extends outward is pivotally supported, the valve shaft cylindrical portion which is connected to the valve rod shaft supporting portion is made of material different from that of the valve body, a slanting surface is formed between the inner peripheral surface and the outer peripheral surface of the sheet ring, an angle and a width formed by the slanting surface and the outer peripheral side surface are the greatest at a position intersecting with the valve shaft at right angles and are the smallest at a position of the valve shaft, a central portion of an inner peripheral surface of the valve body is allowed to project inward to form an engaging projection, the sheet ring is brought into contact with the inner peripheral surface of the valve body under pressure in the opposite sides of the recess groove, the cylindrical bush whose one end is closed is mounted to the other valve rod which pivotally supports the valve element, and the other valve rod is sealed.

TECHNICAL FIELD

The present invention relates to a butterfly valve for opening, closingand controlling a flow passage through which fluid passes. Moreparticularly, the invention relates to a novel improvements of joining avalve body and a valve shaft cylindrical portion which are made ofdifferent kind of material, mounting a sheet ring to an inner peripheralsurface of the valve body, sealing a valve rod which pivotally supportsa valve element, and a gear box of an actuator which drives and rotatesthe valve element.

BACKGROUND ART

A wafer type butterfly valve which is sandwiched and mounted betweenflanges of a pipe to open and close a pipeline is conventionally known.Such butterfly valves are generally used for controlling fluid which issupplied to a plant equipment in various industrial fields.

As such a butterfly valve, there is a proposed structure in which inorder to prevent condensation from being caused on a valve shaftcylindrical portion or an actuator which are opposed to atmosphere dueto a temperature difference between atmospheric air and fluid whichflows through a pipe, the valve shaft cylindrical portion is made ofheat insulator (e.g., synthetic resin) which is different from materialof the valve body so that a temperature of the fluid flowing through thevalve body is not transmitted to the valve shaft cylindrical portion orthe actuator, thereby preventing condensation from being cause. When thevalve body and the valve shaft cylindrical portion are made of differentmaterials, a joining structure therebetween is important. A disk-likevalve element is disposed in the valve body. In order to drive androtate the valve element, a valve rod outwardly extends in the valveshaft cylindrical portion. The valve rod is connected to the actuatorwhich is mounted to an outer end of the valve shaft cylindrical portion.Since a torsional stress is applied to the coupled portion between thevalve body and the valve shaft cylinder, a strong connecting structureis required. Japanese Patent No. 3026251 discloses one example of thebutterfly valve which prevents the condensation. In the butterfly valvedisclosed in this publication, connection grooves and connection legswhich allow connecting portions of the valve body and the valve shaft tofit to each other are disposed around the valve shaft cylindricalportion at distances from one another, the connection grooves and theconnection legs are engaged with each other to ensure the strengthagainst the torsional stress, they are connected to each other usingscrews to prevent the connection legs from coming out from theconnection grooves but they can be separated from each other. In such astructure, however, when the connection leg is fitted into theconnection groove, if there is a gap therebetween, a rattle isgenerated, which may damage the connection groove and the connectionleg. Therefore, precise machinability is required, and a plurality ofconnection grooves and connection legs must be provided around the valveshaft cylindrical portion at equal distances from one another, and thecosts adversely increase.

The valve body comprises a valve body made of rigid material such asmetal which passes through a cylindrical flow passage, a disk-like valveelement which is rotatably pivotally supported by a valve rod in thevalve body, and a sheet ring made of elastic material. The sheet ring isinterposed between an inner peripheral surface of the valve body and thevalve element. An outer peripheral surface of the valve element isbrought into contact with and disengagement from an inner peripheralsurface of the sheet ring to open and close the flow passage. The sheetring of the butterfly valve is made of elastic material. When the valveis closed, the sheet ring is brought into contact with and engagement inthe inner peripheral surface of the sheet ring under pressure, therebysecuring sealing ability, and when the valve is closed, a greatrepulsion is generated by pressure-contact between the sheet ring andthe valve element, and the rotation torque of the valve element isincreased. There is a tendency that the sheet ring is fallen off fromthe valve body by a suction force caused by fluid or by a dragging forcecaused by pressure-contact with the valve element. In order to preventthe sheet ring from falling off from the valve body, there is a proposedstructure in which opposite side surfaces of the sheet ring are fittedto a peripheral side surface of the valve body, the outer peripheralsurface of the sheet ring is mounted to the inner peripheral surface ofthe valve body with a necessary compression margin to exhibitelastically fastening force. Japanese Patent No. 3188680 proposed astructure in which a projecting stripe is provided on a central portionof the outer peripheral surface of the sheet ring, the projecting stripeis fitted into a recess formed in a central portion of an innerperipheral surface of the valve body, thereby preventing the sheet ringfrom moving. In any of the structures, however, the sheet ring isstrongly mounted so that the inner peripheral surface of the valve bodydoes not move. When the valve is closed, elastic repulsion force of thesheet ring when the valve element comes into contact with the innerperipheral surface of the sheet ring becomes great, the rotation torqueof the valve element is increased, and it is difficult to open and closethe valve.

Further, the valve rod which rotatably pivotally supports the valveelement is pivotally supported by a valve rod shaft supporting portionand is extended outward in a radial direction of the valve body. Anactuator is connected to an outer end of one of the valve rods such thatthe actuator can drive and rotate. The other valve rod is sealed by alid body mounted to an outer end of the valve rod shaft supportingportion and is shaft-sealed. One example of the shaft seal apparatus isdisclosed in Japanese Patent Application Laid-open No. 2002-181203.According to the shaft seal apparatus disclosed in this publication, abush is interposed between the valve rod and a valve rod shaftsupporting portion of the valve body, and it is necessary to dispose anO-ring between the bush and the valve rod shaft supporting portion andthe valve rod to seal therebetween, the sealing structure becomescomplicated, it is necessary to fasten a lid body which seals an outerend of the valve rod shaft supporting portion using screws, which istroublesome and inconvenient.

Further, an actuator is connected to one of the valve rods whichrotatably and pivotally supports the valve element to drive and rotatethe valve rod. A manual gear type actuator is generally and widelyemployed as this actuator. According to this manual gear type actuator,a worm gear mechanism in which a worm wheel and a worm are meshed witheach other is incorporated in a gear box, a valve rod is connected tothe worm wheel, a manual handle is connected to the worm, and the valveelement is rotated and driven manually. This manual gear type actuatoris disclosed in Japanese Patent No. 3090420. A gear box of theconventional manual gear type actuator disclosed in this publication isusually a metal molded product such as an aluminum die casting. The gearbox is filled with lubricant which lubricates a worm gear incorporatedin the gear box. A stopper comprises a screw for aligning a valveelement to a fully opened position and a fully closed position to stopworm wheel in a angle of 90 degree rotation range, so that the stopperposition is adjusted. However, in order to effectively utilize abuilding in recent years, the gear box is disposed in a room where anormal work is carried out without providing a machine room undergroundin many cases, and there is a problem that a floor or a wall surface inthe room is contaminated by grease leaking from the gear box. Further,since the adjusting screw is used, a structure of the gear box iscomplicated, and there is also a problem that condensation is caused onan outer surface.

Problems that this Invention is to Solve

First object of this invention is to precisely joint a valve body and avalve shaft cylindrical portion which are made of different materialssuch as metal and synthetic resin using relatively easily machiningoperation, thereby exhibiting sufficient strength against a torsionalstress, and to prevent the valve body and the valve shaft cylindricalportion from falling off from each other using a simple structure.

Second object of the invention is to mount the sheet ring to the innerperipheral surface of the valve body with sufficiently great elasticfastening force, and to stably mount the sheet ring, and to reduce arotation torque of the valve element.

Third object of the invention is to reliably seal a shaft seal of avalve rod which rotatably and pivotally support the valve element with asimple structure.

Fourth object of this invention is to solve problems concerning leakageof grease, generation of condensation and complication of a structurewhich are found in the manual gear type actuator.

Means for Solving the Problems

The present invention provides a butterfly valve in which a cylindricalflow passage is formed in the valve body such as to penetrate the valvebody, a sheet ring made of elastic sealing material is mounted in thevalve body, a disk-like valve element which comes into contact with andseparates from the sheet ring is rotatably and pivotally supported bythe sheet ring, a valve rod shaft supporting portion is formed in aradial direction of the valve body, the valve rod shaft supportingportion pivotally supports valve rods which pivotally support the valveelement, an actuator is connected to an outer end of one of the valverods, thereby driving and rotating the valve element, wherein a portionof the one valve rod which extends outward is pivotally supported, thevalve shaft cylindrical portion which is connected to the valve rodshaft supporting portion is made of material different from that of thevalve body, the ends of the valve shaft cylindrical portion and thevalve rod shaft supporting portion are formed into rectangularcylindrical recess and projection which are fitted to each other, afitting projection and a fitting groove which fit to fitting surfaces ofthe valve shaft cylindrical portion and the valve rod shaft supportingportion are formed, a connection pin is driven into the fitting portionsof the valve shaft cylindrical portion and the valve rod shaftsupporting portion and they are connected to each other in a falling-outpreventing state. Preferably, the valve body is molded using aluminumdie cast, the valve shaft cylindrical portion is molded using syntheticresin having insulative properties, iron-based casting or metal materialwhich is different from that of the valve body. A thickness of an innersurface angle portion of the recess with which an angle portion of theprojection comes into contact upon reception of torsional stress fromthe actuator is made thick, the fitting projection and the fittinggroove are located near this thick angle portion.

A compression margin of the sheet ring with respect to an innerperipheral surface of the valve body is set such that the compressionmargin is small at a central portion of the sheet ring and thecompression margin is great at opposite sides of the sheet ring so thatthe sheet ring is held by the inner peripheral surface of the valve bodyby an elastic fastening force at the opposite sides, the central portionof the sheet ring with which the valve element comes into contact underpressure is allowed to move slightly together with the valve element,and a movable torque of the valve element is reduced. Preferably, aslanting surface is formed between the inner peripheral surface and theouter peripheral surface of the sheet ring, an angle and a width formedby the slanting surface and the outer peripheral side surface are thegreatest at a position intersecting with the valve shaft at right anglesand are the smallest at a position of the valve shaft. A central portionof an inner peripheral surface of the valve body is allowed to projectinward to form an engaging projection, a recess groove into which theengaging projection is formed in the outer peripheral surface of thesheet ring, and the sheet ring is held by engaging the engagingprojection and recess groove with each other. A slanting surface isformed between the inner peripheral surface and the outer peripheralsurface of the sheet ring, an angle and a width formed by the slantingsurface and the outer peripheral side surface are the greatest at aposition intersecting with the valve shaft at right angles and are thesmallest at a position of the valve shaft.

Further, a cylindrical bush whose one end is closed is inserted into theother valve rod, an inner end of the bush is brought into contact withthe sheet ring under pressure to seal the valve rod, and outer end ofthe bush is supported in a falling-out preventing state by means of apin which is driven into the valve rod shaft supporting portion.Preferably, an O-ring is interposed between the bush and the valve rodshaft supporting portion to seal a gap therebetween, and a knob isformed on an outer end of the bush for taking out the bush.

Further, the actuator comprises a coupled body of upper and lower gearboxes in which a manually driven worm gear mechanism is integrallyincorporated in the gear box, both the upper and lower gear boxes aremolded products made of synthetic resin, a stopper portion which limitsa rotation range of the worm gear mechanism is integrally formed in thegear box, one connection peripheries of the upper and lower gear boxesare formed with upper standing walls to which the other peripheries arefitted, the upper standing wall is provided at its outer side with asealing projection.

Further, the invention provides a butterfly valve in which a cylindricalflow passage is formed in the valve body such as to penetrate the valvebody, a sheet ring made of elastic sealing material is mounted in thevalve body, a disk-like valve element which comes into contact with andseparates from the sheet ring is rotatably and pivotally supported bythe sheet ring, a valve rod shaft supporting portion is formed in aradial direction of the valve body, the valve rod shaft supportingportion pivotally supports valve rods which pivotally support the valveelement, an actuator is connected to an outer end of one of the valverods, thereby driving and rotating the valve element, wherein a portionof the one valve rod which extends outward is pivotally supported, thevalve shaft cylindrical portion which is connected to the valve rodshaft supporting portion is made of material different from that of thevalve body, ends of the valve shaft cylindrical portion and the valverod shaft supporting portion are formed into rectangular cylindricalrecess and projection which are fitted to each other, a fittingprojection and a fitting groove which fit to fitting surfaces of thevalve shaft cylindrical portion and the valve rod shaft supportingportion are formed, a thickness of an inner surface angle portion of therecess with which an angle portion of the projection comes into contactupon reception of torsional stress from the actuator is made thick, thefitting projection and the fitting groove are located near this thickangle portion, a connection pin is driven into the fitting portions ofthe valve shaft cylindrical portion and the valve rod shaft supportingportion and they are connected to each other in a falling-out preventingstate, the valve body is molded using aluminum die cast, and the valveshaft cylindrical portion is molded using synthetic resin havinginsulative properties, a slanting surface is formed between the innerperipheral surface and the outer peripheral surface of the sheet ring,an angle and a width formed by the slanting surface and the outerperipheral side surface are the greatest at a position intersecting withthe valve shaft at right angles and are the smallest at a position ofthe valve shaft, a central portion of an inner peripheral surface of thevalve body is allowed to project inward to form an engaging projection,a recess groove into which the engaging projection is formed in theouter peripheral surface of the sheet ring, the sheet ring is broughtinto contact with the inner peripheral surface of the valve body underpressure in the opposite sides of the recess groove, the cylindricalbush whose one end is closed is mounted to the other valve rod whichpivotally supports the valve element, and the other valve rod is sealed.

Effect of the Invention

According to the present invention, the valve body and the valve shaftcylindrical portion are made of different materials, they are connectedwith each other with sufficient strength against the torsional stress,and it is possible to reliably prevent the valve from being damaged bythe torsional stress and to prevent rattle from being generated. Thefalling-out in the axial direction can also be prevented reliably, andit is possible to provide an extremely excellent connection structurebetween the valve body and the valve shaft cylindrical portion made ofdifferent materials.

It is possible to mount the sheet ring to the inner peripheral surfaceof the valve body with sufficiently great elastic fastening force, andto stably mount the sheet ring. A rotation torque of the valve elementcan be reduced.

Further, the shaft seal of the valve rod can be achieved with a simplestructure in which the bush is inserted into the valve rod and is fixedusing a pin. It becomes easy to automate the shaft seal of the valverod.

Further, since the upper and lower gear boxes are molded using syntheticresin, the size precision is enhanced, the stopper can be integrallyformed. Since opening adjusting means by means of a screw is notrequired, the entire structure can be simplified, and the costs can bereduced. Since synthetic resin having insulative properties is used, itis possible to effectively prevent condensation. It is easy to obtain agreaseless structure using resin having higher lubrication ability. Thisgreaseless structure can solve the problem of contamination of a roomfloor and a wall surface caused by leakage of grease, and this structureis extremely beneficial.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an outer appearance of an entirebutterfly valve according to the present invention.

FIG. 2 is an exploded perspective view of the entire butterfly valve.

FIG. 3 is a vertical sectional view of the entire butterfly valve exceptan actuator thereof.

FIG. 4 is a front view of a valve body of a partially cut-away butterflyvalve.

FIG. 5 is a side view of the valve body.

FIG. 6 is a plan view of the valve body.

FIG. 7 is a perspective view of an upper bush.

FIG. 8 is a sectional view of the upper bush.

FIG. 9 is a perspective view of a lower bush.

FIG. 10 is a sectional view of the lower bush.

FIG. 11 is a side view of a partially cut-away sheet ring.

FIG. 12 is a sectional view of the sheet ring taken along a differentline.

FIG. 13 is an enlarged sectional view of an essential portion of amounting structure between the sheet ring and the valve body.

FIG. 14 is a front view of a valve element.

FIG. 15 is a plan view of the valve element.

FIG. 16 is a front view of a valve shaft cylindrical portion.

FIG. 17 is a side view of the valve shaft cylindrical portion.

FIG. 18 is a plan view of the valve shaft cylindrical portion.

FIG. 19 is a bottom view of the valve shaft cylindrical portion.

FIG. 20 is an exploded perspective view of the actuator.

FIG. 21 is a diagram showing an interior of an upper gear box.

FIG. 22 is a sectional view showing details of connected portion betweenupper and lower gear box.

BEST MODE FOR CARRYING OUT THE INVENTION

A preferred mode for carrying out the invention will be explained indetail. The invention is characterized in that a valve body and a valveshaft cylindrical portion are made of different materials such as metaland synthetic resin, and the valve body and the valve shaft cylindricalportion are connected with each other with sufficient strength against atorsional stress and a falling-out. For example, the valve body is madeof metal such as aluminum die cast or casting, and the valve shaftcylindrical portion is made of metal material which is different fromthat of synthetic resin such as nylon ABS, PBT, PPS or the like and thevalve body. The valve body and the valve shaft cylindrical portion areconnected to each other such that substantially angular cylindricalrecesses and projections of the valve body and the valve shaftcylindrical portion are fitted to each other. Opposed fitting surfacesof the recess and the projection are formed with fitting groove andfitting projection which fit to each other. By fitting the fittinggroove and the fitting projection to each other, the valve body and thevalve shaft cylindrical portion are connected to each other withsufficient precision and strength, and it is possible to cope with thetorsional stress, and easy machinability can be achieved.

The number of fitting grooves and the fitting projections may be oneeach, but it is preferable that at least two fitting grooves and fittingprojections are formed on central opposed position of the angularcylindrical shaped recess and the projection to exhibit more reliabledetent function, thereby enhancing strength against the torsionalstress. By fitting the fitting groove and the fitting projection to eachother to exhibit the detent function, the machining precision of theangular cylindrical recess and projection is not especially required,and precision to such a degree that they are fitted to each othertightly in some degree is sufficient. In generally, when two members arefitted to each other and held by angle shape, machining precision offitting surfaces is required, and if the precision is insufficient, agap is generated, a rattle is generated and there is an adversepossibility that the members are damaged. However, it is extremelydifficult to precisely machine the entire fitting surface, andespecially when they are made of different materials, the difficulty isfurther increased, and costs are largely increased.

In this invention, the fitting groove and the fitting projection areprecisely formed, they are fitted to each other to achieve the fittingconnection, and precision in the recess and the projection which areangular cylindrical portions is not required. Therefore, the machiningoperation is easy as compared with a case in which the entire surface ofthe angular cylindrical portion is precisely machined. Since the fittinggroove and the fitting projection which requires precision are grooveand projection having small width and extending in the axial direction,precise machining operation can be carried out relatively easily. In thedie casting or resin formation, since a product is taken out from a die,it is necessary to provide a draft angle. A draft angle of metal isgreater than a draft angle of resin. However, in the case of a limitedspecific portion such as the fitting groove and the fitting projectionof the present invention, the draft angle can be set to zero, and byproviding no draft angle, the precision can be enhanced. In the case ofresin formation, the precision of only the fitting groove is partiallyenhanced to mold. In the case of die cast molding, it is possible topartially enhance the precision of the fitting projection bypost-machining such as shaving working.

According to this invention, it is possible to precisely machine only aportion which needs to be precise, and by fitting the precisely formedfitting groove and fitting projection to each other, it is possible toconnect the valve body and the valve shaft cylindrical portion which aremade of different materials with each other with sufficient strength,and they can be connected to each other with strength which cansufficiently withstands torsional stress applied to the connectedportion therebetween. The connected valve body and valve shaftcylindrical portion are coupled to each other through a connection pinwhich is driven in a direction perpendicular to the axial direction,which prevents the valve body and the valve shaft cylindrical portionfrom separating from each other in the axial direction.

Since the greatest valve-closing driving force is applied to theconnected portion between the valve body and the valve shaft cylindricalportion in the fully closing direction, it is necessary to enhance thestrength of the inner surface angle portion of the recess of the valvebody which collides and contact with the angle portion of the projectionof the valve shaft cylindrical portion in the fully closing rotatingdirection. In the present invention, a thickness of this portion isincreased, the fitting projection formed in the inner surface of therecess is located slightly closer to this thick portion not on a centralportion, and the valve-closing driving force is concentrated on onelocation.

Next, the invention is characterized in that a sheet ring is made ofelastic sealing member which is mounted to an inner peripheral surfaceof the valve body, a central portion of the sheet ring with which thevalve element comes into contact under pressure is mounted to the valvebody with a small compression margin, at least one side, preferably bothsides of the central portion are mounted to the valve body with largecompression margin, the compression margins of the sheet ring to thevalve body are different, so that the sheet ring is strongly mounted tothe valve body on the side having the large compression margin, and thesheet ring is brought into contact with the valve element on the centralportion having small compression margin, thereby reducing the rotationtorque of the valve element.

A central portion of an outer peripheral surface of the sheet ring isformed with a recess groove. The recess groove has such width and depththat an engaging projection formed on an inner peripheral surface of thevalve body is engaged in the recess groove. The recess groove is formedsuch as to surround the outer peripheral surface. An outer diameter ofthe sheet ring does not have size which is not tightly contact with aninner surface of the valve body in its portion of the recess groove(portion A in FIG. 13) and is formed in a gentle contact state. On theother hand, both sides (portions B and C in FIG. 13) of the recessgroove have outer diameters which are tightly contacted with the innerperipheral surface of the valve body, and is formed into a tight contactstate. With this, the sheet ring is inserted and held by the innerperipheral surface of the valve body at the opposite side portions B andC of the recess groove, the sealing ability is exhibited, and in aportion of an angle sheet portion (corresponding to the portion A) withwhich the valve element comes into contact under pressure, as the valveelement comes into contact, the portion A of the sheet ring is allowedto deviate, and it is possible to reduce the rotation torque of thevalve element. That is, since the compression margins of the sheet ringare different in the portions A to C, it is possible to both reduce themutually contradictory torque, and to hold the sealing ability at thesame time. Further, in a central portion having the small compressionmargin, the recess groove provided in the outer peripheral surface ofthe sheet ring is engaged with the engaging projection provided on thecentral portion of the valve body, the projection and the recess grooveare engaged with each other, thereby restraining the sheet ring frommoving, the suction force of fluid and contact with the valve elementprevent the sheet ring from falling off from the valve body. The innerperipheral surface of the sheet ring is formed with an angle sheetportion which projects in a direction of an inner diameter. The outerperipheral surface of the valve element comes into contact with andseats on the angle sheet portion, thereby closing the valve. A width ofthe angle sheet portion is greatest at a position where the angle sheetportion intersects with a valve shaft hole at right angles through whichthe sheet ring passes in a radial direction. The width of the anglesheet portion is gradually reduced as approaching the valve shaft hole,and the width of the angle sheet portion is the smallest in a peripheryof a boss of the valve shaft hole. With this design, the contactpressure with respect to the valve element can substantially beequalized in the entire inner peripheral surface of the sheet ring, thesealing force can be equalized, and it is possible to prevent fluid fromleaking by leakage of seal.

A slanting surface is formed between the inner peripheral surface and anouter peripheral side surface of the sheet ring. An angle between theslanting surface and the outer peripheral side surface and a width ofthe slanting surface are greatest at a position intersecting with thevalve shaft at right angles, and are smallest at a position of the valveshaft. A position intersecting with the valve shaft at right angleswhere the width and angle of the slanting surface are the greatest and aposition of the valve shaft where the width and angle of the slantingsurface are the smallest are connected with each other through a cosinecurve. By forming the slanting surface between the inner peripheralsurface and the outer peripheral surface of the sheet ring, a gapbetween the tip end of the valve element and the inner peripheralsurface of the sheet ring becomes sufficiently wide in a fine opening ofthe valve element, it is possible to reduce the suction force on theside of an orifice which becomes the greatest at the positionintersecting with the valve shaft at right angles in the fine opening,and to reduce the suction amount of the sheet ring as small as possible,and it is possible to prevent the sheet ring from falling off and frombeing damaged.

Further, this invention is characterized in that the valve rod which isrotatably and pivotally supported by the valve rod in the valve body issealed. A valve rod shaft supporting portion extends radially outward ofthe valve body, and the valve rod is pivotally supported by the valverod shaft supporting portion. One of the valve rods passes through thevalve shaft cylindrical portion which is continuous with the valve rodshaft supporting portion and is connected to a desired actuator mountedto an outer end of the valve shaft cylindrical portion and is driven androtated. The other valve rod is an idle side valve rod, this valve rodis located in the valve rod shaft supporting portion, a cylindrical bushwhose lower end is closed is mounted to an outer end of the valve rod ina form of a cap, an opened inner end of the bush is inserted through thesheet ring and sealed. The closed outer end is held in apulling-out-preventing state by means of a pin which is driven into thevalve rod shaft supporting portion so that the shaft seal is maintained.An O-ring is mounted to an outer surface of the bush, and a gap betweenthe outer surface and the valve rod shaft supporting portion is sealed.By the shaft seal structure, the shaft seal of the valve rod can beachieved by such a simple structure that the bush is inserted into thevalve rod and is fixed by means of the pin. Therefore, it is possible toautomate the shaft seal of the valve rod.

Embodiment

Referring to FIGS. 1 and 2, a reference number (1) represents a valvebody made of aluminum die cast which passes through a flow passage(101). A sheet ring (2) made of elastic sealing material such as rubberis detachably mounted in the valve body (1), and sets a substantialdiameter of the flow passage (101). A reference number (3) represents adisk-like valve element which is rotatably and pivotally supported inthe sheet ring (2) by a valve rod (4). By rotating the valve element(3), an outer peripheral surface thereof is allowed to come into contactwith and separated from an inner peripheral surface of the sheet ring(2), thereby opening and closing the flow passage. The valve rods (4)are rotatably and pivotally supported by valve rod shaft supportingportions (102) and (103) which extends radially outward of the valvebody. One of the valve rod (401) extends long from the valve rod shaftsupporting portion (102) through a valve shaft cylindrical portion (5)outward. An actuator (6) which drives and rotates the valve rod isconnected to an outer end of the valve rod (401). The actuator (6) isnot limited to a manual gear type actuator as shown in the drawing, andactuators of various mechanisms such as lever type actuators, electricalactuators, air cylinder type actuators and the like can be employed asthe actuator (6).

The valve body (1) is provided as the aluminum die casting or moldedcasting, and the sheet ring is a vulcanized molded product made ofelastic sealing material such as rubber. The valve element (3) is analuminum die casting like the valve body (1), molded casting,press-worked product. The valve rod (4) is a molded product obtained byshaving a round bar or a product made by a drawing process. The valveshaft cylindrical portion (5) is a synthetic resin molded product suchas nylon, ABS, PBT, PPS and the like. Upper and lower gear boxes (601)and (602) of the actuator, a worm wheel (603), a worm (604) and a handle(605) are molded using synthetic resin like the valve shaft cylindricalportion. It is not always necessary to make the worm wheel (603), theworm (604) and the handle (605) of synthetic resin.

Referring to FIGS. 3 to 6, a cylindrical flow passage (101) passesthrough the valve body (1) made of aluminum die cast, and the valve rodshaft supporting portions (102) and (103) extend from the outerperipheral surface of the flow passage (101) radially outward. Anengaging projection (104) is formed on a central portion of an innerperipheral surface of the valve body such as to surround the innerperipheral surface. The engaging projection (104) has a width which issubstantially half of the inner peripheral surface. The engagingprojection (104) has a compression margin with respect to the sheet ring(2) which is different from compression margins on the opposite sides ofthe engaging projection when the sheet ring (2) is mounted. With thisstructure, the rotation torque of the valve element (3) is reduced.

As shown in FIGS. 4 to 6, a valve rod hole (108) is formed in the valverod shaft supporting portions (102) and (103) such as to penetrate themfrom inside toward outside. The valve shaft cylindrical portion (5) isconnected to the upper valve rod shaft supporting portion (102). Asshown in FIGS. 4 to 6, a recess (105) is formed in an upper end of theupper valve rod shaft supporting portion (102) so that a projection(501) formed on a lower portion of the valve shaft cylindrical portion(5) can be engaged in the recess (105). Fitting projections (106)project from opposed inner peripheral wall surfaces of the recess (105).The fitting projection (106) is fitted into the fitting groove (503)formed in the outer peripheral surface of the projection projecting fromthe lower portion of the valve shaft cylindrical portion (5). Thefitting projection (106) is not provided with a draft angle like thefitting groove (503), so that the fitting projection can be fitted intothe fitting groove precisely. In order to enhance the strength of theinner surface angle portion (107) of the recess (105) to which thegreatest load is applied by collision against the angle portion of theprojection of the valve shaft cylindrical portion (5) when the valve isfully closed, a thickness of this portion is increased. The fittingprojection (106) is provided slightly closer to the thick angle portion(107) rather than the central portion. With this structure, it ispossible to receive all the valve-closing driving force, and to enhancethe strength.

The upper valve rod (401) whose lower end is connected to the valveelement (3) has a necessary length, the upper valve rod (401) passesthrough the upper valve rod shaft supporting portion (102) and the valveshaft cylindrical portion (5) and extends upward, and is driven androtated by the actuator (6) which is connected to an upper end of theupper valve rod (401). The upper valve rod (401) penetrates an upperbush (403) in the upper valve rod shaft supporting portion (102).Referring to FIGS. 7 and 8, the upper bush (403) comprises a shortcylindrical body extending in the vertical direction. The upper bush(403) is formed at its outer peripheral surface with a groove (408) intowhich an O-ring (406) is inserted. The O-ring (406) seals a gap betweenthe upper bush and the inner peripheral surface of the upper valve rodshaft supporting portion (102). Another O-ring (409) is mounted on aninner surface of an upper end of the upper bush (403), and the O-ring(409) seals a gap between the upper valve rod with the inner surface. Agroove (410) is formed in an intermediate portion of the upper valve rod(401). A bifurcated pressing plate (411) is engaged in the groove (410)(see FIG. 2). By connecting the pressing plate (411) to an inner bottomsurface of the recess (105) of the upper valve rod shaft supportingportion (102) by means of screw, the valve rod (401) is prevented fromfalling out.

A short lower valve rod (402) is inserted into the lower valve rod shaftsupporting portion (103) from below and is connected to the valveelement (3). A cylindrical lower bush (404) is inserted into the lowervalve rod (402), and supports a lower surface by a fixing pin (405)driven from a lateral direction and is pivotally supported in afalling-out prevented state. As shown in FIGS. 9 and 10, the lower bush(404) comprises a short cylindrical body, an upper surface of the lowerbush (404) is opened, and a lower surface thereof is closed. The lowerbush (404) is inserted into the lower valve rod (402) from below in aform of a cap, and an upper end of the lower bush (404) is fitted intothe sheet ring (2) and sealed. The bush is formed at its outerperipheral surface with a groove (408) into which the O-ring (406) ismounted. The O-ring (406) seals a gap between the bush and the innerperipheral surface of the lower valve rod shaft supporting portion(103). An angular columnar knob (407) projects from the closed lowersurface, and the bush can easily be taken out using desired graspingmeans such as a nipper, a pincher or the like. Since the bottom surfaceof the lower bush (404) is closed, it is possible to prevent fluid fromleaking out. Because of sealing effect of the O-ring, it is possible toeffectively prevent fluid from leaking toward an outer periphery of thebush and from entering from outside. Further, the opened end of the bush(404) comes into tight contact with the sheet ring and the shaft seal ofthe lower valve rod can be achieved only by inserting the bush into thelower valve rod and driving the fixing pin (405), and the shaft seal ofthe lower valve rod can be automated.

With reference to FIGS. 11 and 12, the sheet ring (2) is made of elasticsealing material such as rubber, and is vulcanized molded. Amountain-shaped sheet portion (201) projecting in a direction of aninner diameter is formed on an inner peripheral surface of the sheetring (2). An outer peripheral surface of the valve element comes intocontact with and seats on an angle sheet portion (201) under pressureand the valve is closed. The valve shaft hole (202) penetrates the sheetring (2) in the radial direction. A width of the angle sheet portion(201) is greatest at a position where the angle sheet portion (201)intersects with the valve shaft hole (202) at right angles, and thewidth is gradually reduced as approaching the valve shaft hole (202),and the width becomes smallest in a boss peripheral edge of the valveshaft hole. With this design, the contact pressure with respect to thevalve element (3) can be equalized substantially in the entire innerperipheral surface of the sheet ring, the sealing force can beequalized, and it is possible to prevent fluid from leaking which may becaused by leakage of the seal.

A slanting surface (203) is formed between the inner peripheral surfaceand the outer peripheral surface of the sheet ring (2). An angle formedbetween the slanting surface (203) and its outer peripheral side surfaceand a width of the slanting surface are greatest at a position where theslanting surface and the valve shaft intersect with each other at rightangles, and are smallest at a position of the valve shaft. A positionintersecting with the valve shaft at right angles where the width andangle of the slanting surface (203) are the greatest and a position ofthe valve shaft where the width and angle of the slanting surface arethe smallest are connected with each other through a cosine curve. Byforming the slanting surface (203) between the inner peripheral surfaceand the outer peripheral surface of the sheet ring (2), a gap betweenthe tip end of the valve element and the inner peripheral surface of thesheet ring (2) becomes sufficiently wide in a fine opening of the valveelement, it is possible to reduce the suction force on the side of anorifice which becomes the greatest at the position intersecting with thevalve shaft at right angles in the fine opening, and to reduce thesuction amount of the sheet ring (2) as small as possible, and it ispossible to prevent the sheet ring (2) from falling off and from beingdamaged. The structure of this sheet ring is disclosed in JapanesePatent No. 3188680 in detail.

A recess groove (204) is formed in a central portion of the outerperipheral surface of the sheet ring (2) such as to surround the outerperipheral surface. The recess groove (204) has such width and depththat the engaging projection (104) formed on the inner peripheralsurface of the valve body is engaged with the recess groove (204). Anouter diameter of the sheet ring (2) does not have size which is nottightly contact with an inner surface of the valve body (1) in itsportion of the recess groove (204) (portion A in FIG. 13) and is formedin a gentle contact state. On the other hand, both sides (portions B andC in FIG. 13) of the recess groove (204) have outer diameters which aretightly contacted with the inner peripheral surface of the valve body(1), and is formed into a tight contact state. With this, the sheet ring(2) is inserted and held by the inner peripheral surface of the valvebody (1) at the opposite side portions B and C of the recess groove(204), the sealing ability is exhibited, and in a portion of an anglesheet portion (corresponding to the portion A) with which the valveelement (3) comes into contact under pressure, as the valve element (3)comes into contact, the portion A of the sheet ring (2) is allowed todeviate, and it is possible to reduce the rotation torque of the valveelement (3). That is, since the compression margins of the sheet ring(2) are different in the portions A to C, it is possible to both reducethe mutually contradictory torque, and to hold the sealing ability atthe same time.

The sheet ring (2) is in a gently contacting state at the portion A, butin the portions B and C, the sheet ring (2) is mounted to and tightlycontacted with the inner peripheral surface of the valve body (1) withsufficient compression ratio. Therefore, it is possible to stronglymount the sheet ring to the valve body at the portions B and C, and thesheet ring is prevented from falling off from the valve body and frombeing damaged by the fluid pressure. The portion A with which the valveelement comes into contact under pressure and seal is achieved is not intight contact with the inner peripheral surface of the valve body, andits movement accompanied by the valve element is allowed when theportion A comes into contact with the valve element (3). As a result,the rotation torque of the valve element becomes small, unnecessarycompression by the valve element is prevented, and only the compressionrequired for sealing is applied to the rubber. Therefore, it is possibleto reduce the compression ratio of the sheet ring, and to prevent therubber from being deteriorated. This makes it possible to use a materialhaving relatively low tear strength such as silicon rubber as the sheetring.

Referring to FIGS. 14 and 15, a basic shape of the valve element (3) isdisk-like shape. As shown in FIG. 15, the valve element (3) is formedinto a slant surface whose thickness is gradually reduced toward itsouter periphery. In a state in which bosses of upper and lower valve rodholes (301) are connected to each other, a vertical rib (302) extendingfrom a center of a surface of the valve element in the axial directionis formed. Three lateral ribs (303), (304) and (305) are formed on asurface of the valve element on the side of a nozzle and on the side ofan orifice such as to extend substantially in parallel to a directionperpendicular to a direction of the valve shaft. Each of the lateralribs (303), (304) and (305) has a constant height from the surface ofthe valve element, and a direction of fluid flowing in the vicinity ofthe valve element surface is controlled using this rib.

That is, a center lateral rib (304) is located at a maximum flowvelocity in the pipe, divides the maximum flow velocity and acceleratesthe flow velocity. The lateral ribs (303) and (305) disposed above andbelow the center rib are inclined toward the center lateral rib, anddirects the fluid in a low speed region near the pipe wall in adirection of the center lateral rib, and its speed is increased in astate in which the fluid is pulled into the flow velocity which isaccelerated by the center rib. With respect to the fluid, the bosses ofthe upper and lower valve rod holes (301) functions as a resistance ofthe flow passage, fluid which collides against the boss generates swirlon a secondary side of the boss, and this further increases the fluidresistance. The three lateral ribs exhibit rectifying effect withrespect to swirl generated on the secondary side of the boss, andreduces generation of swirl. As a result the three lateral ribs dividethe flow velocity in the pipe and rectify the flow, complement aresistance of fluid on the pipe wall and a resistance of fluid on asurface of the valve element by flowing direction control owned by theribs, and reduce the flow resistance of the entire valve.

Referring to FIGS. 2 and 16 to 19, the valve shaft cylindrical portion(5) is a substantially rectangular cylindrical body which is made ofnylon and which has necessary length, and the upper valve rod (401)penetrates inside of the valve shaft cylindrical portion (5) and extendsin the vertical direction. A lower portion of the valve shaftcylindrical portion (5) is formed with the projection (501) which isfitted into the recess (105) formed in the upper valve rod shaftsupporting portion (102). An upper portion of the valve shaftcylindrical portion (5) is formed with a supporting plate (502) on whicha lower gearbox (601) of the actuator (6) is placed and supported. Theprojection (501) has an outer peripheral surface shape corresponding toan inner peripheral surface shape of the recess (105), the innerperipheral surface can be fitted into the outer peripheral surface, thefitting groove (503) into which the projection formed on an innersurface opposed to the recess (105) is fitted is formed in the outerperipheral surface. The fitting groove (503) is aligned to a position ofthe fitting projection (106), and is formed at a position slightlydeviated from the center. A valve rodhole (504) vertically penetratesthe center of the valve shaft cylindrical portion. A pinhole (506) fordriving the connection pin (505) is formed in a surface of theprojection (501) where the fitting groove (503) is not formed. Boltinsertion holes (507) are formed in four corners of the supporting plate(502).

The valve body (1) and the valve shaft cylindrical portion (5) areconnected to each other in such a manner that the fitting projection(106) is first engaged into the fitting groove (503), and the projection(501) on the lower portion of the valve shaft cylindrical portion (5) isdriven into the recess (105) of the upper valve rod shaft supportingportion (102). Next, the connection pin (505) is driven into the uppervalve rod shaft supporting portion (102) and the valve shaft cylindricalportion (5) from a lateral direction, thereby connecting both of them.The upper valve rod shaft supporting portion (102) and the valve shaftcylindrical portion (5) are fitted to each other by rectangularcylindrical shapes of the recess (105) and the projection (501), orprecisely fitted to each other by precise position, size and shape ofthe fitting projection (106) and the fitting groove (503), and bydriving of the connection pin, and it is possible to reliably preventthe torsional stress caused by the actuator (6) and to prevent thefalling out accident, and it is possible to achieve extremely strong andstable connection.

As described above, the recess (105) and the projection (501) sufficeonly if they are fitted to each other using the angle shape, and theyneed not be fitted precisely to each other using the angle shape of theentire connection surfaces, and only the fitting projection (106) andthe fitting groove (503) need to be machined precisely, the number ofparts which need to be precisely machined is small, the machiningoperation is facilitated as a whole, and the costs can be reduced. Theconnection pin is driven to prevent the falling out accident in theaxial direction. Therefore, together with the connection structure forpreventing the torsional stress, it is possible to strongly and stablyconnect the valve body and the valve shaft cylindrical portion made ofdifferent materials such as metal and synthetic resin. As a result, itis possible to produce the valve body having a complicated structure byrelatively easy metal working such as the aluminum die casting, and tomake the valve shaft cylinder of insulative material, and the valve bodyand the valve shaft are connected to form the butterfly valve whichprevents the condensation.

Referring to FIGS. 2 to 20 to 22, the actuator (6) includes the wormwheel (603) which is rotatably and pivotally supported in the gear boxformed by connecting the lower gear box (601) and the upper gear box(602), and the worm (604) which meshes with the worm wheel. An upper endof the upper valve rod (401) is non-rotatably connected to the wormwheel (603), and a handle shaft (606) is connected to the worm (604).The handle (605) is mounted to the outer end of the handle shaft (606).The upper and lower gear boxes have the worm wheel and the worm therein,and are placed on the upper supporting plate (502) of the valve shaftcylindrical portion (5), and bolt and nut are inserted through the gearboxes and the boxes are fastened by the bolt and nut. A reference number(607) represents an opening instructing plate (607) integrally stands onthe worm wheel (603), and the opening instructing plate (607) projectsupward from the upper gear box and shows opening of the valve element.

The upper and lower gear boxes (601) and (602) are made of syntheticresin such as nylon ABS, PBT, PPS or the like. As shown in FIG. 21, astopper (610) for stopping the worm wheel (603) at a fully openingposition and a fully closing position at an rotation angle of 90 degreeis integrally formed in the upper gear box (602). As shown in FIG. 22,an upper standing wall (608) is formed on an upper periphery of thelower gear box (601). The upper standing wall (608) is fitted to theupper gear box. Further, a sealing projection (609) projects outward ofthe upper standing wall (608) at a slight distance therefrom. Becausethe upper standing wall (608) exists, it is possible to easily andreliably combine the upper and lower gear boxes. The sealing projection(609) abuts against a lower surface of the upper gear box, and when theyare fastened by bolt and nut, the sealing projection (609) is fittedinto the lower surface, and sealing ability is exhibited. When a packingis interposed therebetween, the sealing projection compresses thepacking, and reliable sealing effect can be obtained.

Since the entire upper and lower gear boxes are molded using syntheticresin, the size precision is enhanced, and the opening stopper (606) canbe integrally formed. As a result, opening adjusting means by means of ascrew is not required unlike the conventional technique, the entirestructure can be simplified, and the costs can be reduced. Sincesynthetic resin having insulative properties is used, it is possible toeffectively prevent condensation. It is easy to obtain a greaselessstructure using resin having higher lubrication ability. Recently, abutterfly valve of this kind is disposed in a room. From a point of viewof this situation, the fact that grease is charged into the gear box cansolve the problem of contamination of a room floor and a wall surfacecaused by leakage of grease, and this structure is extremely beneficial.

1. A butterfly valve in which a cylindrical flow passage is formed inthe valve body such as to penetrate the valve body, a sheet ring made ofelastic sealing material is mounted in the valve body, a disk-like valveelement which comes into contact with and separates from the sheet ringis rotatably and pivotally supported by the sheet ring, a valve rodshaft supporting portion is formed in a radial direction of the valvebody, the valve rod shaft supporting portion pivotally supports valverods which pivotally support the valve element, an actuator is connectedto an outer end of one of the valve rods, thereby driving and rotatingthe valve element, wherein a portion of the one valve rod which extendsoutward is pivotally supported, the valve shaft cylindrical portionwhich is connected to the valve rod shaft supporting portion is made ofmaterial different from that of the valve body, ends of the valve shaftcylindrical portion and the valve rod shaft supporting portion areformed into rectangular cylindrical recess and projection which arefitted to each other, a fitting projection and a fitting groove whichfit to fitting surfaces of the valve shaft cylindrical portion and thevalve rod shaft supporting portion are formed, a connection pin isdriven into the fitting portions of the valve shaft cylindrical portionand the valve rod shaft supporting portion and they are connected toeach other in a falling-out preventing state.
 2. A butterfly valveaccording to claim 1, wherein a compression margin of the sheet ringwith respect to an inner peripheral surface of the valve body is setsuch that the compression margin is small at a central portion of thesheet ring and the compression margin is great at opposite sides of thesheet ring so that the sheet ring is held by the inner peripheralsurface of the valve body by an elastic fastening force at the oppositesides, the central portion of the sheet ring with which the valveelement comes into contact under pressure is allowed to move slightlytogether with the valve element, and a movable torque of the valveelement is reduced.
 3. A butterfly valve according to claim 1, wherein acylindrical bush whose one end is closed is inserted into the othervalve rod, an inner end of the bush is brought into contact with thesheet ring under pressure to seal the valve rod, and outer end of thebush is supported in a falling-out preventing state by means of a pinwhich is driven into the valve rod shaft supporting portion.
 4. Abutterfly valve according to claim 1, wherein the actuator comprises acoupled body of upper and lower to gear boxes in which a manually drivenworm gear mechanism, both the upper and lower gear boxes are moldedproducts made of synthetic resin, a stopper portion which limits arotation range of the worm gear mechanism is integrally formed in thegear box, one connection peripheries of the upper and lower gear boxesare formed with upper standing walls to which the other peripheries arefitted, the upper standing wall is provided at its outer side with asealing projection.
 5. A butterfly valve according to claim 1, whereinthe valve body is molded using aluminum die cast, and the valve shaftcylindrical portion is molded using synthetic resin having insulativeproperties.
 6. A butterfly valve according to claim 1, wherein the valveshaft cylindrical portion is molded using iron-based casting or metalmaterial which is different from that of the valve body.
 7. A butterflyvalve according to claim 1, wherein a thickness of an inner surfaceangle portion of the recess with which an angle portion of theprojection comes into contact upon reception of torsional stress fromthe actuator is made thick, the fitting projection and the fittinggroove are located near this thick angle portion.
 8. A butterfly valveaccording to claim 2, wherein a slanting surface is formed between theinner peripheral surface and the outer peripheral surface of the sheetring, an angle and a width formed by the slanting surface and the outerperipheral side surface are the greatest at a position intersecting withthe valve shaft at right angles and are the smallest at a position ofthe valve shaft.
 9. A butterfly valve according to claim 2, wherein acentral portion of an inner peripheral surface of the valve body isallowed to project inward to form an engaging projection, a recessgroove into which the engaging projection is engaged is formed in theouter peripheral surface of the sheet ring, and the sheet ring is heldby engaging the engaging projection and recess groove with each other.10. A butterfly valve according to claim 2, wherein a slanting surfaceis formed between the inner peripheral surface and the outer peripheralsurface of the sheet ring, an angle and a width formed by the slantingsurface and the outer peripheral side surface are the greatest at aposition intersecting with the valve shaft at right angles and are thesmallest at a position of the valve shaft.
 11. A butterfly valveaccording to claim 3, wherein an O-ring is interposed between the bushand the valve rod shaft supporting portion to seal a gap therebetween.12. A butterfly valve according to claim 3, wherein a knob is formed onan outer end of the bush for taking out the bush.
 13. A butterfly valvein which a cylindrical flow passage is formed in the valve body such asto penetrate the valve body, a sheet ring made of elastic sealingmaterial is mounted in the valve body, a disk-like valve element whichcomes into contact with and separates from the sheet ring is rotatablyand pivotally supported by the sheet ring, a valve rod shaft supportingportion is formed in a radial direction of the valve body, the valve rodshaft supporting portion pivotally supports valve rods which pivotallysupport the valve element, an actuator is connected to an outer end ofone of the valve rods, thereby driving and rotating the valve element,wherein a portion of the one valve rod which extends outward ispivotally supported, the valve shaft cylindrical portion which isconnected to the valve rod shaft supporting portion is made of materialdifferent from that of the valve body, ends of the valve shaftcylindrical portion and the valve rod shaft supporting portion areformed into rectangular cylindrical recess and projection which arefitted to each other, a fitting projection and a fitting groove whichfit to fitting surfaces of the valve shaft cylindrical portion and thevalve rod shaft supporting portion are formed, a thickness of an innersurface angle portion of the recess with which an angle portion of theprojection comes into contact upon reception of torsional stress fromthe actuator is made thick, the fitting projection and the fittinggroove are located near this thick angle portion, a connection pin isdriven into the fitting portions of the valve shaft cylindrical portionand the valve rod shaft supporting portion and they are connected toeach other in a falling-out preventing state, the valve body is moldedusing aluminum die cast, and the valve shaft cylindrical portion ismolded using synthetic resin having insulative properties, a slantingsurface is formed between the inner peripheral surface and the outerperipheral surface of the sheet ring, an angle and a width formed by theslanting surface and the outer peripheral side surface are the greatestat a position intersecting with the valve shaft at right angles and arethe smallest at a position of the valve shaft, a central portion of aninner peripheral surface of the valve body is allowed to project inwardto form an engaging projection, the sheet ring is brought into contactwith the inner peripheral surface of the valve body under pressure inthe opposite sides of the recess groove, the cylindrical bush whose oneend is closed is mounted to the other valve rod which pivotally supportsthe valve element, and the other valve rod is sealed.
 14. A butterflyvalve according to claim 2, wherein a cylindrical bush whose one end isclosed is inserted into the other valve rod, an inner end of the bush isbrought into contact with the sheet ring under pressure to seal thevalve rod, and outer end of the bush is supported in a falling-outpreventing state by means of a pin which is driven into the valve rodshaft supporting portion.
 15. A butterfly valve according to claim 2,wherein the actuator comprises a coupled body of upper and lower to gearboxes in which a manually driven worm gear mechanism, both the upper andlower gear boxes are molded products made of synthetic resin, a stopperportion which limits a rotation range of the worm gear mechanism isintegrally formed in the gear box, one connection peripheries of theupper and lower gear boxes are formed with upper standing walls to whichthe other peripheries are fitted, the upper standing wall is provided atits outer side with a sealing projection.
 16. A butterfly valveaccording to claim 3, wherein the actuator comprises a coupled body ofupper and lower to gear boxes in which a manually driven worm gearmechanism, both the upper and lower gear boxes are molded products madeof synthetic resin, a stopper portion which limits a rotation range ofthe worm gear mechanism is integrally formed in the gear box, oneconnection peripheries of the upper and lower gear boxes are formed withupper standing walls to which the other peripheries are fitted, theupper standing wall is provided at its outer side with a sealingprojection.
 17. A butterfly valve according to claim 2, wherein thevalve body is molded using aluminum die cast, and the valve shaftcylindrical portion is molded using synthetic resin having insulativeproperties.
 18. A butterfly valve according to claim 3, wherein thevalve body is molded using aluminum die cast, and the valve shaftcylindrical portion is molded using synthetic resin having insulativeproperties.
 19. A butterfly valve according to claim 4, wherein thevalve body is molded using aluminum die cast, and the valve shaftcylindrical portion is molded using synthetic resin having insulativeproperties.
 20. A butterfly valve according to claim 2, wherein thevalve shaft cylindrical portion is molded using iron-based casting ormetal material which is different from that of the valve body.
 21. Abutterfly valve according to claim 3, wherein the valve shaftcylindrical portion is molded using iron-based casting or metal materialwhich is different from that of the valve body.
 22. A butterfly valveaccording to claim 4, wherein the valve shaft cylindrical portion ismolded using iron-based casting or metal material which is differentfrom that of the valve body.
 23. A butterfly valve according to claim 5,wherein the valve shaft cylindrical portion is molded using iron-basedcasting or metal material which is different from that of the valvebody.
 24. A butterfly valve according to claim 2, wherein a thickness ofan inner surface angle portion of the recess with which an angle portionof the projection comes into contact upon reception of torsional stressfrom the actuator is made thick, the fitting projection and the fittinggroove are located near this thick angle portion.
 25. A butterfly valveaccording to claim 3, wherein a thickness of an inner surface angleportion of the recess with which an angle portion of the projectioncomes into contact upon reception of torsional stress from the actuatoris made thick, the fitting projection and the fitting groove are locatednear this thick angle portion.
 26. A butterfly valve according to claim4, wherein a thickness of an inner surface angle portion of the recesswith which an angle portion of the projection comes into contact uponreception of torsional stress from the actuator is made thick, thefitting projection and the fitting groove are located near this thickangle portion.
 27. A butterfly valve according to claim 5, wherein athickness of an inner surface angle portion of the recess with which anangle portion of the projection comes into contact upon reception oftorsional stress from the actuator is made thick, the fitting projectionand the fitting groove are located near this thick angle portion.
 28. Abutterfly valve according to claim 6, wherein a thickness of an innersurface angle portion of the recess with which an angle portion of theprojection comes into contact upon reception of torsional stress fromthe actuator is made thick, the fitting projection and the fittinggroove are located near this thick angle portion.
 29. A butterfly valveaccording to claim 8, wherein a central portion of an inner peripheralsurface of the valve body is allowed to project inward to form anengaging projection, a recess groove into which the engaging projectionis engaged is formed in the outer peripheral surface of the sheet ring,and the sheet ring is held by engaging the engaging projection andrecess groove with each other.
 30. A butterfly valve according to claim8, wherein a slanting surface is formed between the inner peripheralsurface and the outer peripheral surface of the sheet ring, an angle anda width formed by the slanting surface and the outer peripheral sidesurface are the greatest at a position intersecting with the valve shaftat right angles and are the smallest at a position of the valve shaft.31. A butterfly valve according to claim 9, wherein a slanting surfaceis formed between the inner peripheral surface and the outer peripheralsurface of the sheet ring, an angle and a width formed by the slantingsurface and the outer peripheral side surface are the greatest at aposition intersecting with the valve shaft at right angles and are thesmallest at a position of the valve shaft.
 32. A butterfly valveaccording to claim 11, wherein a knob is formed on an outer end of thebush for taking out the bush.